Custom ecobee thermostat adapter

I’ve wanted a smart thermostat for a while but live in an apartment with a fixed (no remote control), mains powered thermostat. Unfortunately all of the smart thermostats are designed for American HVAC systems which mostly use a 24vac system. I ended up buying an ecobee3 lite and a few things to make an adapter.

3x 24vac relays to switch the mains (240v) control signals.
1x 24vac power adapter to power the ecobee and the relays.
1x fuse and fuse holder for safety.

Basically one relay was wired up to switch each of the heating, cooling and low fan speed control signals. The 24vac side was attached to the ecobee to the relevant terminals (cooling - y, heating - w, fan - g). The 24vac relay was hooked up to the ecobee “R” and “C” terminals.

After it was hooked up and power was turned back on the ecobee booted up. It asked me if it detected the correct wiring (yes). Then I connected it to the wifi and it spent a few minutes calibrating it’s sensors and then it sprung into action cooling our apartment.

Version 2 will have a small pcb with everything mounted on It for better safety and reliability. I’ll also include a small 24vac transformer so no external power adapter will be needed (that’s how it’s currently connected).

Here’s the old thermostat:

Thermostat adapter:

Thermostat installed (with adapter behind, ie inside wall):

Hi…We have both the Nest and Ecobee in our house. Although Nest is a lot nicer aesthetically, Ecobee has all the bells and whistles. If you are the geeky type go with an Ecobee and you’ll get to tweak things a lot more than what Nest offers.
Also, I would say look into energy programs with your local utility company. I ended up receiving $75 just to participate where they remotely suggest a specific temperature during energy peaks. You can override it manually if the suggested temperature is not comfortable for you. So far we participated in 3 of these surges, and the suggested temperature was 76 degrees which is not that uncomfortable for us.